The nervous system serves as the body control center and communications electrical-chemical wiring network. As a key homeostatic regulatory and coordinating system, it detects, interprets, and responds to changes in internal and external conditions. The nervous system integrates countless bits of information and generates appropriate reactions by sending electrochemical impulses through nerves to effector organs, such as muscles and glands. The brain and spinal cord are the central nervous system (CNS); the connecting nerve processes to effectors and receptors serve as the peripheral nervous system (PNS). Special sense receptors provide for taste, smell, sight, hearing, and balance. Nerves carry all messages exchanged between the CNS and the rest of the body.
A nerve is an enclosed, cable-like bundle of axons (long, slender projections of neurons) in the peripheral nervous system. Nerves provide a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons to peripheral organs. Each nerve is covered externally by a dense sheath of connective tissue known as the epineurium. Underlying the epineurium is a layer of flat cells, the perineurium, which forms a complete sleeve around a bundle of axons. Perineurial septae extend into the nerve and subdivide it into several bundles of fibers. Surrounding each fiber is the endoneurium, which consists of an inner sleeve of material called the glycocalyx and an outer, delicate, meshwork of collagen fibers. Damage to nerves can be caused by physical injury or swelling (e.g. carpal tunnel syndrome), autoimmune diseases (e.g. Guillain-Barré syndrome), infection (neuritis), diabetes or failure of the blood vessels surrounding the nerve.
Repairing damaged nerves is hampered by several factors, including damage to the protective sheathing that surrounds nerves, gaps between the proximal and distal stumps of severed nerves and the limited ability of damaged nerves to regenerate. Tubes or conduits for guiding peripheral nerve regeneration are commonly made of materials such as polylactide, polylactide/polyglycolide copolymers, acrylic copolymers, performed mesothelial tubes or various other synthetic polyesters. The shortcomings of using a tube or conduit made of these materials include, for example, immune response, induction of scar tissue, and difficulty in application.
Thus, there remains a need for materials and techniques that provide a safe, effective means of repairing damaged or otherwise traumatized nerves in the body.